1. Field of Invention
The present invention relates to an apparatus for a liquid crystal display. More particularly, the present invention relates to a structure of a color filter.
2. Description of Related Art
Liquid crystal is a material having properties between those of crystal and liquid. The alignment of the liquid crystal molecules varies in response to external stimulation such as an electrical field generated by an applied voltage. Hence, this feature of the liquid crystal molecules can be utilized to create a display unit.
A color thin film transistor liquid crystal display (TFT-LCD) is produced in current technology by separately fabricating a thin-film-transistor (TFT) array substrate and a color filter substrate and then assembling them together. The color filter substrate includes three color filters of red, green and blue, and black matrixes. The black matrixes shield the thin film transistors, wirings on the indium tin oxide (ITO), and some portions of the display area adjacent to electrodes. The portions adjacent to electrodes generally experience light leak problems because of non-uniform electric field distributions or in-plane electric fields. In addition, the main functions of the black matrixes are to increase contrast of display and to prevent light from damaging the thin film transistors, so the black matrixes must have optical characteristics of low reflectivity and high optical density.
FIG. 1 is a schematic view of a conventional liquid crystal display panel structure. A thin film transistor 106 is located on a thin film transistor substrate 102, and the thin film transistor 106 is in charge of changing voltage to control an alignment direction of liquid crystals 108. Black matrixes 118 are under the thin film transistor 106, and the black matrixes 118 are usually formed by a metal 112 and an oxide 114. Today, chromium and chromium oxide are usually used to form the black matrixes 108. Color filters 120a are located between the black matrixes 118, and filter light from a light source 110 into red, green and blue light in different regions. Moreover, the foregoing black matrixes 118 and the color filters 120a are all located on the substrate 104.
Generally, the conventional black matrixes of the metal/oxide structure experience problems of excessive reflection of external light and insufficient light shading. The thin film transistor is very sensitive to light, and easily generates a light current by a little light that affects its operation; moreover, more light may damage the thin film transistor. Insufficient light shading does not provide a good light shading for the thin film transistor, and makes a base color of the display panel appear only as dark blue, not black, which is able to improve contrast in vision. The excessive reflection of external light lowers the visibility of the liquid crystal display, and causes inconvenience in using it.